Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, The Chinese Academy of Sciences, Wuhan 430074, PR China; The University of Chinese Academy of Sciences, Beijing 10049, PR China.
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, PR China.
Sci Total Environ. 2017 Aug 15;592:608-615. doi: 10.1016/j.scitotenv.2017.03.042. Epub 2017 Mar 16.
There are increasing concerns in nitrogen (N) pollution worldwide, especially in aquatic ecosystems, and thus quantifying its sources in waterways is critical for pollution prevention and control. In this study, we investigated the spatio-temporal variabilities of inorganic N concentration (i.e., NO, NH) and total dissolved N (TDN) and identified their sources in waters and suspended matters using an isotopical approach in the Jinshui River, a river with a length of 87km in the monsoon-climate region of China. The spatio-temporal inorganic N concentrations differed significantly along the longitudinal gradient in the river network. The NO, NH and TDN concentrations ranged from 0.02 to 1.12mgl, 0.03 to 4.28mgl, and 0.33 to 2.78mgl, respectively. The N tracing studies demonstrated that N in suspended organic matter was in the form of suspended particulate nitrogen (SPN) and was primarily from atmospheric deposition and agricultural fertilizer. In contrast, N in stream waters was mainly in the form of nitrate and was from atmospheric deposition, fertilizers, soil, and sewage. Meanwhile, both δN-SPN and δN-NO peaked in the rainy season (i.e., July) because of higher terrigenous sources via rain runoff, demonstrating the dominant diffusive N sources in the catchment. Thus, our results could provide critical information on N pollution control and sustainable watershed management of the riverine ecosystem in monsoon-climate region.
人们对全球范围内的氮（N）污染越来越关注，尤其是在水生态系统中，因此量化水系中的氮污染源对于污染预防和控制至关重要。在这项研究中，我们采用同位素方法，调查了中国季风气候区 87 公里长的金水河流域水中和悬浮物中无机氮浓度（即 NO、NH）和总溶解氮（TDN）的时空变化，并确定了它们的来源。该河网的纵向梯度存在显著的时空无机氮浓度差异。NO、NH 和 TDN 的浓度范围分别为 0.02 至 1.12mg/L、0.03 至 4.28mg/L 和 0.33 至 2.78mg/L。氮示踪研究表明，悬浮物中的氮以悬浮颗粒态氮（SPN）的形式存在，主要来自大气沉降和农业肥料。相比之下，水中的氮主要以硝酸盐的形式存在，来源于大气沉降、肥料、土壤和污水。同时，由于雨水径流带来更高的陆源物质，δN-SPN 和 δN-NO 在雨季（即 7 月）达到峰值，表明流域中扩散型氮源占主导地位。因此，我们的研究结果可为季风气候区河流生态系统的氮污染控制和可持续流域管理提供重要信息。
